Composite electrode

ABSTRACT

An electrode for applying electric fields to a patient includes a plurality of ceramic elements (e.g., ceramic discs) that are designed to be positioned against the patient&#39;s skin. Electrical connections are made to the ceramic elements (e.g., using a flex circuit). Temperature sensors (e.g., thermistors) are preferably provided at at least some of the ceramic elements to sense the temperature at the skin beneath the ceramic elements, so that appropriate action can be taken if an overtemperature condition is detected.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application is a continuation of U.S. application Ser. No.11/856,277, filed Sep. 17, 2007, which is incorporated herein byreference.

BACKGROUND

U.S. Pat. Nos. 7,136,699 and 7,146,210, each of which is incorporatedherein by reference, describe treating tumors or other rapidly dividingcells with AC electric fields at particular frequencies and fieldstrengths. This application relates to an improved electrode that isparticularly well-suited for applying those electric fields.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a set of electrodes being used to apply electric fields toa subject.

FIG. 2 is a mechanical schematic diagram of an electrode in accordancewith a first embodiment of the invention.

FIG. 3A is a cross section view of a subsection of the electrode shownin FIG. 2.

FIG. 3B is an exploded cross section view of the same subsection of theelectrode.

FIG. 3C is a rear view of the same subsection of the electrode.

FIG. 4 is an electrical schematic of the electrode shown in FIG. 2.

FIG. 5 is a perspective view of the electrode shown FIG. 2 together witha preferred set of accessories for use therewith.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 depicts a set of electrodes 10 that are used to apply electricfields to a body part 15 of a subject. Each of the electrodes 10 has atlead 11 associated therewith. As described in US Application No.2005/0209642, which is incorporated herein by reference, a preferredapproach for treating tumors using electric fields is to sequentiallyapply the field to the body part 15 being treated in differentdirections in an alternating pattern. One preferred approach to applyingthe field in different directions is to applying the field between afirst set of electrodes for a period of time (e.g., ¼ second), thenapplying a field between a second set of electrodes for a period of time(e.g., ¼ second), then repeating that cycle for an extended duration(e.g., over a period of days or weeks). For example, with the electrodeconfiguration depicted in FIG. 1, a horizontal electric field F_(A) canbe induced in the body part 15 by applying an AC voltage between theleft and right leads 11 using an appropriate voltage source. Similarly,a vertical electric field F_(B) can be induced in the body part 15 byapplying an AC voltage between the top and bottom leads 11 using thesame (or a different) voltage source.

FIG. 2 is a mechanical schematic diagram of a preferred embodiment ofeach of the electrodes 10. The electrode 10 includes a plurality ofceramic elements 20, each of which is preferably disc shaped. Theceramic elements 20 are preferably arranged in an array. Note that whileFIG. 2 illustrates a 3×3 array of ceramic elements 20, arrays of othersizes maybe substituted therefor, such as a 2×2 array or a 2×3 array.

The ceramic elements 20 must be mechanical supported and electricalconnections must be made to each element. A wide variety of approachescan be readily envisioned for mechanically supporting and electricallymaking connections to the ceramic elements 20. One preferred approachthat performs both of these functions is to use a flex circuit 24 toboth mechanically support the ceramic element 20 and provide theelectrical connections. However, a wide variety of alternativeapproaches can be readily envisioned, including but not limited todiscrete wiring, ribbon cable, etc.

Preferably, temperature sensors 22 are incorporated into the electrode10, so that appropriate action (e.g., shutting off or lowering the ACvoltage, or sounding an alarm) can be taken if an overtemperaturecondition is detected. In the illustrated embodiment a temperaturesensor 22 is provided at each of the ceramic elements. However, inalternative embodiments temperature sensors may be provided only atselected ones of the ceramic elements 20. For example, when a 3×3 arrayof ceramic elements 20 are used, a temperature sensor may be providedfor the eight outer ceramic elements 20, and omitted for the centerceramic element. When a flex circuit 24 is used to provide theelectrically connection to the ceramic element, additional traces mayprovided on the flex circuit to interface with the temperature sensors22.

FIG. 3A is a cross section view of one of the ceramic elements 20 with atemperature sensor 22. Each of the ceramic elements 20 preferably has aconductive backing on the side that faces away from the patient, andthis conductive backing is electrically connected to a contact on theflex circuit 24 using any conventional technique (e.g., solder). Theconductive backing of the ceramic elements 20 may be implemented byusing a ceramic disc that is silvered on one side. A cap 26 ispreferably provided to mechanically support each of the ceramic elements20. The caps are preferably made of an insulating material e.g.,plastic.

In one preferred embodiment, the ceramic elements 20 are implementedusing EC99 discs that are about 2 cm in diameter and are silvered on theside that faces away from the patient. In alternative embodiments, theceramic discs 20 are implemented using ceramic discs that are betweenabout 1.5 cm and about 2.5 cm, with a capacitance of art least 10 nF perdisc, so as to provide an array with a capacitance of at least 120 nF.In alternative embodiments, higher capacitance discs may be used (e.g.,at least 15 or at least 20 nF per disc). Preferably, the resistance ofthe ceramic discs should be as high as possible, and they should have adielectric breakdown voltage of at least 4000 V.

Preferably, the ceramic elements 20 and the caps 26 have holes at theircenters that are sized to accommodate the temperature sensors 22. Thetemperature sensors are preferably positioned in these holes, and theleads are mounted and electrically connected to respective traces on theflex circuit 24.

In some preferred embodiments, a thermistor is used as the temperaturesensor, in which case two solder connections are needed to connect eachthermistor to the flex circuit 24—one for each lead. However, personsskilled in the relevant arts will appreciate that a wide variety ofalternative temperature sensors other than thermistors may also be used,including but not limited to temperature sensing integrated circuits,RTDs, etc. In some preferred embodiments, type NTC thermistors in asurface-mount package are used, with a nominal resistance value of 10 kΩat 25° C. The operating range is preferably wide enough to sense theexpected range temperatures (e.g., from 20-50° C.). Of course, wideroperating ranges (e.g., −40° C. to 150° C.) may also be used.

FIG. 3B is an exploded view of the same components depicted in FIG. 3B,and FIG. 3C is a rear view of the same components. Note, however, thatin the FIG. 3C view, the ceramic disc 20 and the temperature sensor 22are obscured by the cap 26.

FIG. 4 is an electrical schematic depicting how the various componentsof the electrode are connected, in an embodiment where the temperaturesensors are implemented using thermistors. The main lead 11 is connectedto one side of each of the ceramic elements 20, and the other side ofeach of the ceramic elements 20 is exposed for placement against thepatient's body. When a pair such electrodes are applied to a patient'sbody, an AC voltage is applied between the main lead 11 of a firstelectrode and a main lead (not shown) of a similar electrode (notshown). An electric field is generated between the ceramic elements ofthe first electrodes (depicted in FIG. 4) and the second electrode (ofsimilar configuration). As discussed above, temperature sensors 22 arepreferably provided at some or all of the ceramic elements. Preferably,the temperature sensors are configured so that an individual temperaturereading can be obtained from each temperature sensor 22. One way toimplement this in embodiments that use thermistors for the temperaturesensors is to route a lead 42 from one end of each of the thermistors toexternal circuitry (not shown), and use a common return lead 44 that isshared by all the thermistors. Any conventional circuitry forinterfacing with the thermistors may be used.

Of course, persons skilled in the relevant arts will recognize that whenalternative temperature sensors are used, the electrical interface tothe temperature sensor will have to be adjusted accordingly from the onedepicted in FIG. 4. For example, if temperature sensing integratedcircuits that communicate over a serial interface bus are used, anappropriate power supply and serial bus must be provided, theimplementation of which will be apparent to persons skilled in therelevant arts.

FIG. 5 depicts an electrode that is similar to the electrode 10discussed above in connection with FIGS. 2-4, together with a preferredset of accessories for use therewith. The electrode 50 is preferablypackaged with a layer 52 of biocompatible hydrogel (e.g., Amgel AG603)disposed beneath each of the ceramic discs, and the ceramic discspreferably rest in a filler layer 54 (e.g., 3M 1773 foam tape) with anadhesive bottom and cutouts dimensioned to accept the ceramic discs. Alayer of adhesive tape 56 (e.g., 3M 1776 non-woven medical tape) ispositioned above the electrode 50, with the adhesive side facing downtowards the patient. The adhesive tape 56 preferably extends laterallybeyond the electrode 50 and the filler layer 54. A peel-away backing 58(e.g., #53 white poly-coated kraft paper) is provided beneath all theother components 52-56. To use the electrode, the backing 58 is peeledaway, which exposes the bottom of the hydrogel layer 52, the adhesivebottom of the filler layer 54, and uncovered portions of the adhesivetape 56. That entire assembly is then pressed against the patient's skin(which has preferably been shaved) so as to adhere thereto. Anelectrical connection is then made to the electrode 50 using anappropriate electrical connector.

While the present invention has been disclosed with reference to certainembodiments, numerous modifications, alterations, and changes to thedescribed embodiments are possible without departing from the scope ofthe present invention, as defined in the appended claims. Accordingly,it is intended that the present invention not be limited to thedescribed embodiments, but that it has the full scope defined by thelanguage of the following claims, and equivalents thereof.

I claim:
 1. A composite electrode comprising: a plurality of ceramicelements, each of the ceramic elements having (a) a lower surfaceconfigured to rest on a patient's body and (b) an upper surface with aconductive backing disposed thereon; a first lead; at least oneelectrical conductor configured to make a direct electrical connectionbetween the upper surface of each of the ceramic elements and the firstlead; and a support structure configured to mechanically connect theplurality of ceramic elements during use, with the lower surface of eachof the plurality of ceramic elements resting on the patient's body. 2.The composite electrode of claim 1, further comprising at least onetemperature sensor configured to sense the temperature beneath at leastone of the ceramic elements.
 3. The composite electrode of claim 1,wherein the least one electrical conductor and the support structure areboth implemented using a flex circuit.
 4. The composite electrode ofclaim 1, wherein the plurality of ceramic elements comprises at least 4ceramic elements.
 5. The composite electrode of claim 1, wherein theplurality of ceramic elements comprises at least 4 ceramic discs, eachhaving a diameter between about 1.5 cm and about 2.5 cm and acapacitance of at least 20 nF, and wherein the least one electricalconductor and the support structure are both implemented using a flexcircuit.
 6. The composite electrode of claim 5, further comprising atleast two thermistors configured to sense the temperature beneath atleast two of the ceramic discs, respectively.
 7. The composite electrodeof claim 5, further comprising a covering disposed above the ceramicelements and the support structure, the covering having an adhesivelower surface that is configured to hold the ceramic elements and thesupport structure against the patient's body.
 8. The composite electrodeof claim 7, wherein the ceramic elements rest in a filler layer with anadhesive bottom and cutouts dimensioned to accept the ceramic elements.9. The composite electrode of claim 8, further comprising at least onetemperature sensor configured to sense the temperature beneath at leastone of the ceramic elements.
 10. The composite electrode of claim 9,wherein the ceramic elements are disc-shaped and are silvered on theirupper surface.
 11. The composite electrode of claim 1, wherein theplurality of ceramic elements consists of nine ceramic discs, eachhaving a diameter between about 1.5 cm and about 2.5 cm and acapacitance of at least 20 nF, wherein the least one electricalconductor and the support structure are both implemented using a flexcircuit, and wherein the composite electrode further comprises at leastfour thermistors configured to sense the temperature beneath at leastfour of the ceramic discs, respectively.
 12. The composite electrode ofclaim 1, wherein the direct electrical connection between the uppersurface of each of the ceramic elements and the first lead is made usinga flex circuit that is soldered to the conductive backing.
 13. Acomposite electrode comprising: at least four ceramic elements, each ofthe ceramic elements having (a) a lower surface configured to rest on apatient's body and (b) an upper surface with a conductive backingdisposed thereon; a first lead; at least one electrical conductorconfigured to make a direct electrical connection between the uppersurface of each of the ceramic elements and the first lead; and asupport structure configured to mechanically connect the ceramicelements during use, with the lower surface of each of the ceramicelements resting on the patient's body; at least two temperature sensorsconfigured to sense the temperature beneath at least two of the ceramicelements, respectively; a layer of electrically conductive hydrogeldisposed on the lower surface of each of the ceramic elements; acovering disposed above the ceramic elements and the support structure,the covering having an adhesive lower surface that is configured to holdthe ceramic elements and the support structure against the patient'sbody.
 14. The composite electrode of claim 13, further comprising abacking disposed beneath the ceramic elements, the support structure,and the covering, wherein the adhesive lower surface of the covering iseasily removable from the backing.
 15. The composite electrode of claim13, wherein the temperature sensors comprise thermistors.
 16. Thecomposite electrode of claim 13, wherein the least one electricalconductor and the support structure are both implemented using a flexcircuit.
 17. The composite electrode of claim 13, wherein there are 9ceramic elements.
 18. The composite electrode of claim 13, wherein thereare 9 ceramic elements that are each round and have a diameter betweenabout 1.5 cm and about 2.5 cm and a capacitance of at least 20 nF, andwherein the least one electrical conductor and the support structure areboth implemented using a flex circuit, and wherein there are at leastfour temperature sensors configured to sense the temperature beneath atleast four of the ceramic elements, respectively.
 19. The compositeelectrode of claim 18, wherein the ceramic elements rest in a foamfiller layer with an adhesive bottom and cutouts dimensioned to acceptthe ceramic elements.
 20. The composite electrode of claim 18, whereinthe ceramic elements are disc-shaped and are silvered on their uppersurface.
 21. The composite electrode of claim 20, wherein the ceramicelements have holes in their centers and the temperature sensors arepositioned in the holes.
 22. The composite electrode of claim 13,wherein the ceramic elements are disc-shaped and are silvered on theirupper surface.
 23. The composite electrode of claim 22, wherein theceramic elements have holes in their centers and the temperature sensorsare positioned in the holes.
 24. The composite electrode of claim 13,wherein the ceramic elements rest in a filler layer.
 25. The compositeelectrode of claim 13, wherein the ceramic elements rest in a fillerlayer with an adhesive bottom and cutouts dimensioned to accept theceramic elements.
 26. The composite electrode of claim 13, wherein theceramic elements rest in a foam filler layer with an adhesive bottom andcutouts dimensioned to accept the ceramic elements.
 27. The compositeelectrode of claim 13, wherein the direct electrical connection betweenthe upper surface of each of the ceramic elements and the first lead ismade using a flex circuit that is soldered to the conductive backing.